Linking to the viewers may be a good usuability practice, but does little to aid in accessibility. MS Word Reader is only partially accessible meaning that when using screen reader and this tool together, you can read very simple pages but not tables or a page with complex formatting. The MS Excel and Power Point readers are not 508 compliant and not accessible. Microsoft's response is they can't understand why a person just would not convert the page to HTML. Simple, in a good many cases the HTML page will not be accessible or meet the 508 standards or accessible-- and this method usually produces a web page with bloated code.

In my opinion, any page where you choose to link to powerpoint documents, excel documents, and possibly even Word documents (depending on complexity and design) without providing an accessible version along with the linked document, the web page does not meet 508 requirements. Specifically Standard M states "When a web page requires that an applet, plug-in or other application be present on the client system to interpret page content, the page must provide a link to a plug-in or applet that complies with §1194.21(a) through (l)." The MS PowerPoint and Excel viewers do not comply with §1194.21(a) through (l). A person who uses assistive technology, such as JAWS, aand who does not have a full version of PowerPoint or Excel on their computer, will not be able to read the linked documents as the PowerPoint and Excel documents as the viewers are not accessible. This means that it is a good usability/accessibility practice to provide an accessible alternative when posting links to these types of documents on your web site.

It was just pointed out to me that I should be adding a link to
download the MS Word Viewer on any page that has a link to a MS Word
document, just as I currently add the link to download Acrobat Reader
for any page with a link to a PDF. Is this common practice? I'm
worried that there are different versions of Word Reader depending on
the version of MS Word, there doesn't appear to be a MacIntosh
version and no persistent link location, etc. I see that there are
other Viewers for Excel and Power Point, and wonder how accessible
any of these applications are.

Our college lets faculty post PDF, MS Word, rtf, or txt, Excel or csv
files, to make materials available to their students. I've always
added the Acrobat Reader download link, but never linked to a plug-in
for text or spreadsheet files. It seems slightly different from a
PDF, since Word and Excel documents download and are not usually
displayed in the browser. Although I have noticed that on my PC
Internet Explorer is displaying MS Word files in a browser mode (but
of course I have the MS Word application on my machine). Other
browsers are not likely to have that feature.

Alternatively, I could restrict links to html or PDF documents, but
often faculty want the student to use the MS Word file as a working
document for an assignment. Many faculty simply find it easier to
post the MS Word document than convert it to PDF or HTML, so I have
lots of these.

I'd be interested in what the group is providing on web pages with
links to content like MS Word or Excel files.